Impacto da implantaçao de perímetros irrigados na qualidade das águas superficiais da porção mineira do médio São Francisco

Abstract

The irrigation projects Jaíba Gorutuba and Laguna Grande located in the mining portion of the Middle San Francisco, occupying an irrigable area of approximately 31,493 ha. As irrigated agriculture has the potential to contaminate water resources due to deforestation, the application of fertilizers and pesticides, the objective of this research was to investigate the impact of irrigation on surface water quality in the region, using secondary data source for monitoring available the Mining Institute of Water Management (IGAM) and HIDROWEB. We selected nine monitoring stations in the region that represented the use and occupation of land for agriculture, conservation areas and urbanized, with the aim of characterizing the impact. We first performed a multivariate analysis (cluster analysis) in an attempt to highlight the monitoring stations similar, considering the physico-chemical and biological weapons. Later tests were nonparametric (Kruskal-Wallis ANOVA and median test, followed by multiple comparisons test) to check which parameters showed different behaviors between the monitoring stations. Finally, we applied the test of the hypothesis of stationarity Spearman, to detect temporal trends present in a data series, aiming to evaluate the increasing trend of the constituents over time. The results of this study was not possible to observe patterns of contamination depending on the location of the stations. However, it was possible to detect that the stations located along the Sao Francisco River showed no significant differences between them, although the use and occupation were different, probably due to greater self-purification capacity of the river São Francisco, in relation to other courses water. The results of the Spearman Rank Correlation test showed that most of the data analyzed in the nine were non-stationary stations, ie, had a tendency to increase or decrease over the monitored period. However, a greater number of data comprising a series longer, it is necessary to confirm this tendency. Considering the effect of seasonality, it was found that during the dry period occurs, in general, a reduction in water quality due to higher concentrations of constituents due to the lower flow of the Rio Verde Grande. It was concluded that in general there was a deterioration in water quality during the study period, depending on the parameters.